Electric furnace.



c.,A. CADWELL ELECTRIC FURNACE. KPPLIQATION man MAY 1, 1915.

Patented Jan. 14,1919.

2 SHEETS-SHEET I.

Mia eased C. A. CADWELL.

ELECTRIC FURNACE. APPLICATION FILED MAY I. 19|5.-

Patented Jan. 14, 1919.

2 SHEETS SHEET 2.

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(LI/7F? egxs 66 owe/(M iimi ' UNITED STATES PATENT OFFICE.

CHARLES A. CADWELL, .OF CLEVELAND, OHIO, ASSIGNOR TO THE ELECTRIC {RAILWAY IMPROVEMENT COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

ELECTRIC FURNACE.

contemplated applying that principle, so as to distinguish it from other inventions.

The present improved furnace is particularly adapted for operating with an electric current of high voltage such as would naturally be employed in the melting and superheating of copper ;for bondlng purposes,

along the line of an electric railroad, and

in other analogous situations.

For such a purpose, a device of this. type is highly desirable since the current can be obtained direct from the trolley wire or third rail of an electric railway, thus obviating the ne- -cessity of having an expensive bonding ear for Welding the'bonds to the rails, which is the prevailing method at present used Where a permanent and homogeneous union between bond and rail is desired. The invention also relates to a method of using such improved furnace to secure the best economy and continuity of operatlon. To the accom- Y plishmentof the foregoing and related ends,

saidinvention, then, consists of the means and steps hereinafter fully described and particularly pointed outin the claims.

The annexed drawings and the following description set forth in detail certain mech-. anism and steps embodying the invention, such disclosed means and steps constituting,

however, but one of various mechanical forms in which the principle of the invention may be used In said annexed drawmgsz- Figurel is a plan view of my improved furnace; Flg. 2 is a centralvertical sectlon on the line 2.-2 in Fig. 1; Fig. 3 is a diagramma'tic view showing two furnaces suitably connected for operation by my; preferred method; Fig. t is a longitudinal section through an improved type of resistance element adapted for use with my furnace on line 4-4 in Fig. 3; Fig. 5 is a transverse section through the same, as indicated by the line 55, Fig. 4; Fig. 6 is a'longitudinal section through-the electrode shown in Fig.-

fipecification of Letters Patent.

l; and Fig. 7 is adiagrammatic illustration of a modified form of the furnace.

. In such drawings, there is shown a casing 1, constituting the furnace chamber, such casing being of any desired shape althou h a convenient shape for this purpose wou ld be the elliptical one here shown. The sides of this casing will be lined with a suitable Patented Jan. 14, 1919.;

Application filed May 1, 1915. Serial No. 25,151.

heat resisting medium, such as magnesite,

for example, which forms the walls 1 proper, while a layer '1 of fire sand resting on a-fire tile foundation l 'constitutes the bottom of such chamber. The top of the latter is partially closed by a more or less permanent cover 1? having an a erture over -Wl110l1 may be placed a remova le cover 1.

suitably supported so as to depend within this chamber are two spaced electrodes 2,

although more electrodes may be used, said electrodes being adjustable vertically by means of threaded spindles 4 provided with hand Wheels 4, and carrying clamp arms 5, in which the'electrodes 2 are mounted. De-v sirably, said spindles 4 will be operatively connected as by sprockets 4 and a sprocket chain 4, so that rotation of 'the one will serve simultaneously to rotate the other. Other types of adjusting means may of coursebe employed. for this purpose.

The bottom layer '1" of the furnace is covered in turn by a layer 6 of material, preferably granularcarbon, or some similar conducting material of relatively high resistance, which may be termed a resistor, and will continue to serve its proper function even though it may become 'caked by the action of the, heat, or it may be made in the form of a cake,'as might for instance be preferable where carborundum is used as such resistor. Upon this resistor, there. are placed one or more crucibles 9, adapted to receive the metal which is to be melted.

The. electrodes 2 will be connected in a suitable electrical circuit including any suitable source of current, either alternating or direct, ,(the latter being illustrated), such for example as the generator for supplying pp plained. The lead to one such electrode, is passed a number of times around the furshown in Fig. 3, as will be presently exnace 1, as indicated, forming a coil 8. By virtue of this coil, which is designated as a magnetic means in the claims, the arcs which occur between the carbon electrodes and the granular carbon layer'6 forming the bottom of the furnace, are affected in such a way that the resistance ofthe arc path of the current is greatly increased, the arc is steadied and any tendency to deviate from the direction of the path designed is overcome, as also the tendency for such are to become extinguished owing to sudden variations in voltage inthe current supplied, or from variations in the resistance of the furnace path, due to the resistor.

Regulation of the intensity of such magnetic field likewise serves to bring the lengths of the arcs under control, and permits such lengths to be varied by the direct adjustment of the electrodes 2 through operation ofthe hand wheels 4.

Since the electrodes of course become very highly heated at their own ends, their upper ends, which are exposed to the air, may also' approach a temperature where slow combustion willtake place- I accordingly find it advantageous to inclose the same in a protecting coat 3 of fire-resisting material, as for example a mixture of fire-clay and graphite which will serve as a conductor and at the same time burn away at the lowerv a5 a standard rheostat with its resistance subend, as the carbon core, forming the elec-K;

trode, proper, is slowly consumed.

It is desirable that the carbon, which is, I a conductor of heat as well as electricity} and which is consumed by combustion if exposed to the air when heated, be protected in some such manner. I

In Fig. 3, I illustrate diagrammatically the method of connecting up two of my furnaces as they will ordinarily be used. As there shown, the leads 7 of the furnaces are connected in series in a circuit 10, supplied with current from asuitable generator 11,; or other source of current. In such circuit I connect a resistance 12 of any desired type, although a very compact and satisfactory type, shown in Figs. land 5, will preferably be employed. This resistance may be optionally connected into the circuit, or left out, by a switch 13, as will be readily understood.

When it is desired to start such two furnaces, this resistance is put into the circuit and all of the electrodes 2 are lowered so as to make contact with the resistor 6. The current is then turned on and its flow is controlled by the resistance of the granular material of the bottoms of the furnaces and the outside resistance 12, there being no arcs. The flow of current being. thus established, the quantity of current flowing may be varied lay-increasing or decreasing the resistance 12, which may be in the form of granular resistor.

of the operator.

ject to switchboard control. When the flow is satisfactory, all the electrodes are raised a portion of the normal amounts, which action adds to the total resistance of the circuit and reduces the amount of the current flowing. The beneficial effect of the coil is here much in evidence in that the amount of currentflowing may be reduced to a remarkable minimum-without danger of exhowever, it is found that the voltage available is not sufiicient to operate both furnaces at maximum efliciency, the electrodes of only one at a time will be raised to produce, arcs of greatest intensity. Thus" the furnaces may be adjusted to utilize current,

of any kind and of any voltage. The usual case for the purposeof bonding rails will be the utilization of 600 volt DC current, the most useful form being'two furnaces in series, each utilizing one half the 600 volt pressure. If, however, two furnaces, adjusted to utilize 600 volt current, be in service along the line of a railroad and it is found that the voltage is lower than the amount above stated, in one of the furnaces,

the electrodes may be not raised, but left in contact with or relatively close to the The total resistance of the circuit when the furnaces are in full operation would, in such a case, be less than that of the original design, by the-amount of the resistance of the arcs of this furnace. The amount of heat generated in this furnace would be small; while the second furnace would befmeanwhile in normal operation, with a resistance measured by 300 volts for which the furnace was originally designed.

i The first furnace, operated in this manner, may be called a preheating furnace, and the operations within the two furnaces will be interchanged or alternated at the pleasure In case one'furnace becomes unfit for use, the other maybe continued in operation by raising the electrodes so that arcs of maximum length and resist-' granular carbon in amount depending upon the amount of resistance desired. Carbon electrodes 16, adapted to be connected in the of the box and these electrodes furnish means by which the resistance unit is placed into the electric circuit. The heat generated by" the passage of the electric current is greatest along the bottom of the box. For this reason, the bottom liningl? of the box is preferably made of magnesite, which is a conductor of heat and provision is made for dissipating the heat of the bottom of the box by circulation of air throu h apertures 18 disposed transversely of the box just below the surface of the bottom as shown in the figure. The total radiating surface of the resistance unit is thus largely increased and the radiation may take place with these surfacesata red heat without injuring any art; A p In usin r the furnace with direct current, the direction-of the current will preferably be reversed after each heat in order to secure even wear on the electrodes and on the walls of thefurnace chamber, but as'hereinbefore indicated,- an alternating current can be used, in whiclnevent this will not be necessary. The present apparatus is adapted to operate witharcs from 2 to 6 inches long depending on the Yvoltage drop across the furnace. The crucibles and metal contained 30 therein areheated by radiation from the furnace walls and from the top and bottom of the furnace, by radiation from the arcs difeet, and by conduction from the resistor bed upon which the crucibles are placed. It has been found in actual practice that two crucibles each containing 20 lbs. of copper can be brought-to a temperature of 2500 degrees in 20 minutes, "which makes the furnaces peculiarly adapted for melting copper for the purpose of bonding where it is essential that no time be lost in bring the metal to a welding heat.

Although in the preferred design shown, the electrodes enter at the top of the furnace and are placed in a vertical position, I do not limit myself to such an arrangement as they could be introduced at the ends or sides and might be horizontal or inclined. Also in the design shown, the resistor is upon the bottom of the furnace, butI do not limit myself to such location as the walls may .be made of a suitable material so as to act wholly or in conjunction with theinaterial on the bottom of the furnace in the present design, as the resistor. Both these modifications in construction'are illustrated in Fig. 7, where two electrodes 20 it will be-seen,

7 enter each end wall of the urnace chamber,

while two resistor bodies 21 are disposed along the respective sides of such'chamber.

Other modes of applying the principle of my invention ,may be employed instead of the one explained, change being made as regards the mechanism and steps herein d isclosed, provided the means or steps any such stated means or steps be employed.

' a. I therefore particularly point out and dis tinctly claim as my invention 1- 1. In a furnace, the combination of a suitable chamber; electrodes extending therein; a resistor within said chamber, said electrodes and resistor being so disposed relatively to each other that arcs are formed from one electrode to said resistor and from the latter to the other electrode; and an electromagnetic coil surrounding said furnace so as to produce a magneticfield adapted to direct and steady such arcs.

. 2. In a furnace,-the combination of a suit,- able chamber; electrodes extending therein; a resistor within said chamber, said electrodes and resistor being so disposed relatively toeach other that arcs are formed from one electrode to said resistor and from the latter to the other electrode, saidielectrodes and resistor being adjustable with respect to each other so as to vary the lengths of said arcs; and means for directing and steadying such arcs.

3. In a furnace, the combination of a suitable chamber; electrodes extending therein;

a resistor within said chamber, said electrodesand resistor being so disposed relatively to each other that arcs are formed from one electrode to said resistor and from the latter to the other electrode, said electrodes being adjustable toward and from said resistor so as to vary the lengths of said arcs; and means for directing andsteadying such arcs. v

4. Ina furnace,.the combination of asuitable chamber; electrodes-extending therein; a resistor within said chamber, said electrodes and resistor being so disposed relatively to .each other that arcs are formed from one electrode to said resistor and from the latter to. the other electrode, said electrodes being simultaneously adjustable toward and from said resistor so as to vary the lengths of said arcs; and magnetic means for directing and steady-ing such arcs.

5. In a furnace, the combination of a. suitable chamber; electrodes extending therein;

a resistor within said chamber, said electrodes and resistor being so disposed rela tively to each other that arcs are formed from one electrode to said resistor andfrom; the latter to the other electrode, said elee-- current to said electrodes, whereby arcs are" formed between said electrodes respectively. and the bottom of said chamber; and means for directing and steadying such arcs for increasing'the electrical resistance of the same. 7. In a furnace the combination of a suit able chamber having a bottom of granular high-resistance conducting material; electrodes adjustably mounted in said chamber above such bottom; means for supplying current to said electrodes, whereby arcs are formed between said electrodes respectively and the bottom of said chamber; and magnetic means for directing and steadyingsuch arcs, thus permitting themto'be lengthened and for increasing the electrical resistance of the same in addition to the increase produced by lengthening.-

8. In a furnace, the combination of a suit-' able chamber having a bottom of granular high resistance conducting material; electrodes adjustably mounted in'said chamber above such bottom; means for supplying current to said electrodes, whereby arcs are formed between said electrodes respectively and the' bottom of said chamber; a coil mounted around said chamber to give a magnetic field for directing and steadying such arcs; and means for simultaneously: adju'st ing said two electrodes; n v i 9. In a furnace, the combination of a suitable chamber having a bottom of granular high-resistance conducting-,material; electrodes adjustably mounted in said chamber above such bottom; means for adjusting said to be lengthened and for increasing the elec-.

trical resistance of the same in addition to the increase produced by lengthening.

' 10. In electric furnace operations, the combination of two furnaces connected in series, said furnaces having adjustable electrodes, one of said furnaces being adapted to be used as a rheostat and having only a low degree of heat generated therein, and being adapted for use as a preheating furnace.

11. In electric furnace operation, the combination of two furnaces connected in series, said furnaces having adjustable electrodes whereby the amount of heat generated may be varied, one of said furnaces being adapted to act as-a rheostat and preheating furnace during heating operation of second furnace, said second furnace then-being adjusted to act as rheostat and preheating furnaceduring final heatingv operation of said first furnace.

Signed by me, this 30th day of April, 1915.

' oHARL'Es A. CADWELL.

Attested by+ D. F. DAVIS, JNO. F. OBERLIN. 

